Today, NASA scientist David Des Marais gave a talk titled "The Potential for Habitable Environments in the Basaltic Plains and Columbia Hills of Gusev Crater, Mars" at the 117th annual meeting of the Geological Society of America in Salt Lake City, Utah. Snip from an online abstract:
# Habitable environments must provide, among other things, chemical building blocks, sources of biochemical energy and conditions that maintain liquid water at least intermittently. Gusev basalts resemble compositionally olivine basalts on Earth that can support life deep beneath the seabed.
# Rocks along the western slopes of Husband Hill have been extensively altered and chemical constituents have been added and/or removed. These indicate higher water/rock values that might have sustained life. Life can survive in subsurface darkness by obtaining energy from redox reactions such as iron oxidation.
# Rocks indicate that at least some deposits in Husband Hill might have sustained habitable environments in the distant past.
Link.